[s4e15] The Benefactor Factor Page

Leonard is initially repulsed by the idea of "selling himself" for science, but Sheldon is surprisingly supportive, viewing it as a logical sacrifice for the advancement of physics.

When Leonard seeks advice from Penny, she finds the situation hilarious and encourages him to do it, teasing him about being a "gigolo" for science. [S4E15] The Benefactor Factor

Title reference: Mrs. Latham, a woman Leonard has sex with so that she will donate money to the university. Leonard is initially repulsed by the idea of